The US Army currently employs six types of infantry: light infantry (consisting of four sub-types), "Stryker infantry", and mechanized infantry. The infantrymen themselves are essentially trained, organized, armed, and equipped the same, save for some having airborne, air assault, and/or Ranger qualification(s), the primary difference being in the organic vehicles (or lack thereof) assigned to the infantry unit, or the notional delivery method (i.e., parachute drop or heliborne) employed to place the infantryman on the battlefield. All modern US Army rifle platoons contain three nine-man rifle squads, with each type of infantry having a discrete TO&E.

The United States Army Aviation Branch is the administrative organization within the United States Army responsible for doctrine, manning and configuration for all aviation units.
After the United States Army Air Corps grew into the Army Air Forces and split into the new service, the United States Air Force, the Army was left with its sole fixed-wing aviation units flying L-2 observation planes for artillery units. The Army would develop a new concept of aviation using the helicopter that would show promise during the Korean War and would revolutionize warfare during the Vietnam War.